Abstract
Simple SummaryThe present study investigated the emergence, antimicrobial susceptibility profiles, serotypes, and genotypes of Salmonella enterica from hatcheries and their upstream breeder farms to determine the occurrence of antimicrobial-resistant (AMR) Salmonella enterica contamination in hatcheries and its dissemination in an integrated broiler chicken operation. The hatcheries showed a high prevalence of Salmonella isolates with high antimicrobial resistance and no susceptible isolate. The AMR isolates from hatcheries originating from breeder farms could disseminate to the final retail market along the broiler chicken supply chain. Hatcheries play a more important role than breeder farms in the occurrence and spread of Salmonella in the broiler production chain. The emergence of AMR Salmonella in hatcheries may be due to the horizontal spread of resistant isolates rather than the first contamination of susceptible Salmonella and acquisition of resistance. Therefore, Salmonella control in hatcheries, particularly its horizontal transmission, is important.Positive identification rates of Salmonella enterica in hatcheries and upstream breeder farms were 16.4% (36/220) and 3.0% (6/200), respectively. Among the Salmonella serovars identified in the hatcheries, S. enterica ser. Albany (17/36, 47.2%) was the most prevalent, followed by the serovars S. enterica ser. Montevideo (11/36, 30.6%) and S. enterica ser. Senftenberg (5/36, 13.9%), which were also predominant. Thirty-six isolates showed resistance to at least one antimicrobial tested, of which 52.8% (n = 19) were multidrug resistant (MDR). Thirty-three isolates (enrofloxacin, MIC ≥ 0.25) showed point mutations in the gyrA and parC genes. One isolate, S. enterica ser. Virchow, carrying the blaCTX-M-15 gene from the breeder farm was ceftiofur resistant. Pulsed-field gel electrophoresis (PFGE) showed that 52.0% S. enterica ser. Montevideo and 29.6% S. enterica ser. Albany isolates sourced from the downstream of hatcheries along the broiler chicken supply chain carried the same PFGE types as those of the hatcheries. Thus, the hatcheries showed a high prevalence of Salmonella isolates with high antimicrobial resistance and no susceptible isolate. The AMR isolates from hatcheries originating from breeder farms could disseminate to the final retail market along the broiler chicken supply chain. The emergence of AMR Salmonella in hatcheries may be due to the horizontal spread of resistant isolates. Therefore, Salmonella control in hatcheries, particularly its horizontal transmission, is important.
Highlights
Salmonellosis, caused by Salmonella enterica (S. enterica), is among the most frequently reported foodborne bacterial diseases [1]
The susceptibility breakpoints of most antimicrobials were interpreted based on the Clinical and Laboratory Standard Institute (CLSI) guidelines [31], whereas those of the antimicrobials used for the animals, including ceftiofur, enrofloxacin, and florfenicol, were interpreted based on the CLSI standards document VET-01 [32]
There was a significant difference (p < 0.05) in isolation rates among the breeder farm and hatchery; there were no significant differences in isolation rates among the cloacal swabs samples (1/125, 0.8%) and the litter samples (5/75, 6.7%) in the breeder farms
Summary
Salmonellosis, caused by Salmonella enterica (S. enterica), is among the most frequently reported foodborne bacterial diseases [1]. The critical role of a hatchery in disseminating Salmonella to commercial broiler farms and possibly exposing breeder flocks to contamination on egg trays, trolleys, and vehicles has been previously reported [20,21,22]. Most of these works have focused on the potential for cross-contamination and infection caused by Salmonella in chicks during incubation.
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